Ambulatory Blood Pressure Monitor: Purpose & Use

Ambulatory blood pressure monitor is a medical device for measuring blood pressure periodically over an extended time period. The monitor, in general, is compact and lightweight and can be comfortably worn by a patient during night and day. The data can be stored and saved in a computer for further analysis.

Why use ambulatory blood pressure monitoring

• Screening for "white-coat" hypertension
• Tracking morning surge in blood pressure
• Better correlation with end-organ damage than with clinic blood pressure readings
• Better prediction for cardiovascular events and mortality than clinic readings
• Monitoring of nocturnal (sleep) blood pressure for patients with hypertension - high nocturnal readings (< 10% lower than daytime average) would be a cause for concern.
• 24-hour monitoring which allows assessment of clinic effects, drug effects, work influence, etc.

White-coat hypertension is a condition in which people experience high blood pressure only when they are in the doctor's office. This is attributed to the fact some people do get nervous or anxious because of the examination. People who experience the white-coat hypertension have an elevated systolic blood pressure between 140 and 180 mmHg while at the doctor's office and a "normal" blood pressure in other situations. This is a common phenomenon (20+%) and may lead to unnecessary treatments.

Morning surge is the difference between the mean systolic blood pressure during the two hours after walking and arising minus the mean systolic blood pressure during the hour that included the lowest blood pressure during sleep. There is a significant increase in risk for stroke, heart attack and sudden death during the morning surge hours. This is also true after an afternoon siesta. Knowing the morning surge would help in adjusting the medicine and in modifying patient's behavior.

Optimal blood pressure control requires a smooth reduction in the entire 24-hour day. Blood pressure varies during a day and it is not clear which reading (daytime mean, night-time mean, 24-hour mean, morning surge, ambulatory blood pressure load...) gives the best prognosis. The blood pressure measured during a patient's workday is a good predictor of left ventricular hypertrophy, and there is supporting evidence for a carryover of high daytime ambulatory blood pressure into the evening period in patients with "high demand, low control" types of work.

People with very high blood pressure during exercise are most likely to develop high blood pressure, according to a study published in American Journal of Hypertension (April 2004). They are likely to have arteries that do not expand as much as normal arteries when blood is pumped to them. Blood pressure can go up to 200/80 during running and 300/200 during very heavy weight lifting for a normal person. Readings significantly above the 200 range is a good indicator for potential future problems. Consider going into a program (diet and exercise) for heart attack prevention if you have high readings during exercise.

When ambulatory blood pressure monitor should be used

• To exclude "white coat" hypertension in patients with newly discovered hypertension with no evidence of end-organ damage
• In patients with borderline or labile hypertension
• To monitor blood pressure during exercise
• To assist blood pressure management in patients whose blood pressure is apparently poorly controlled, despite using appropriate antihypertensive therapy
• In patients with worsening end-organ damage, despite adequate blood pressure control on office blood pressure measurements
• To assess adequacy of blood pressure control over 24 hours in patients at particularly high risk of cardiovascular events, in whom rigorous control of blood pressure is essential (eg, diabetes, past stroke)
• In deciding on treatment for elderly patients with hypertension
• In patients with suspected syncope or orthostatic hypotension
• In patients with symptoms or evidence of episodic hypertension
• In hypertension in pregnancy